Serpens Cauda constellation. Optical image of the constellation Serpens Cauda. Serpens is a constellation of the northern hemisphere. It is split into two non-contiguous parts, Serpens Caput (Serpent Head) to the west and Serpens Cauda (Serpent Tail) to the east. Between these two halves lies the constellation of Ophiuchus, the Serpent-Bearer. Part of the Milky Way's galactic plane passes through Serpens Cauda, which is therefore rich in deep-sky objects such as the Eagle Nebula and star cluster Messier 16.